In a radio frequency circuit section of a cell phone, a transmitting circuit and a receiving circuit are selectively connected to a common antenna through a switch circuit for radio frequency signals. A switch element of such a switch circuit for radio frequency signals has conventionally been based on a high electron mobility transistor (HEMT) made of compound semiconductor. Recently, it has been under consideration in view of requirements for cost reduction and downsizing that the HEMT will be replaced with a metal oxide semiconductor field effect transistor (MOSFET) formed on a silicon substrate.
However, the conventional MOSFET formed on a silicon substrate has large parasitic capacitance between a source or drain electrode and the silicon substrate. Another problem is that the radio frequency signal incurs large power loss because silicon is a semiconductor. In this context, a technique is proposed in which a switch circuit for radio frequency signals is formed on an silicon on insulator (SOI) substrate.
In a radio frequency switch based on MOSFET, for example, to achieve radio frequency characteristics (such as insertion loss and ON distortion/OFF distortion) required for cell phones, it is necessary to generate an appropriate gate potential inside the radio frequency switch.
However, such a voltage generator is limited in current supply capacity because of restriction on the layout area. Hence, if a cross current over the current supply capacity occurs in the load of the voltage generator at power-on, there is a possibility of an incorrect operation in which the voltage generator fails to reach the desired potential.